As the technology of magnetic data storage and retrieval matures, the demands on speed and accuracy of data transfer has reduced the size of constituent parts, increased magnetic flux, operating current, voltage and speed of operations resulting in an increased tendency of components to fail.
Magnetic read/write heads commonly used in high-density magnetic data storage devices provide both reading and writing capability. Such structures are often fabricated using modern production techniques beginning with chip fabrication. In such manufacturing techniques, substructures such as the read sensor and write magnetic components are fabricated into the chip in a closely associated fashion typically in the substrate material. The read/write components are integrated into the chip with a variety of substructures used to ensure that the read/write functions occur without interference, and that the read/write components can communicate with active components in the drive and ultimately the computing equipment. The writing capability places magnetic information on the surface of a recording medium, while the reading capability obtains information from magnetic domains in the recording medium created by the writing function. In both the reading and writing function, electrical components are formed using conventional fabrication techniques. At a minimum, these techniques obtain reading structures in the form of shielded sensors fabricated into insulating material. Similarly a writing structure typically comprises opposite magnetic poles defining the write gap. The read sensors and the magnetic polar structures are typically formed in insulating materials.
The tendency of insulating materials to acquire and hold static or electric charges, electric fields, etc., is well known. The resistivity of an insulator is typically at least about 1015 ohm-cm. The acquisition and discharge of built up charges on insulating surfaces including static charges can result in damage in a variety of electrical components, particularly those subject to damage from relatively high voltage. Like, many other micro scale structures, magneto resistive sensors in modern magnetic recording heads are susceptible to damage from discharge of stray electric charges, fields, and currents. Requirements for increasing area storage densities exacerbate this problem due to the decreasing size of head features increase magnetic flux and other increases in the demands of technology. Protection from electrostatic discharge (ESD) events in magnetic recording heads during head fabrication or production, drive assembly, installation and throughout customer use is therefore a large and growing concern.
Although ESD failures vary widely, this invention specifically addresses two important classes of ESD failure: dielectric breakdown and breakdown from charged device events. During various stages of magnetic recording head production, the head is exposed to high impedance charge sources that readily break down thin dielectrics (such as half gap dielectrics) while posing little risk to low resistance elements such as coils, poles, vias and the magnetic recording element itself. Additionally, damage to the read element itself may occur during downstream production if the product becomes charged. Since the slider body itself is isolated from the read element by layers of insulator, charge residing on the read element may be retained indefinitely, only to be quickly and destructively dissipated through the read element at the moment of contact to the reader or writer leads from any outside body.
We understand that conventionally ESD is prevented in some structures using conductive pathways. These structures and methods of using these structures, having a resistivity of less than 104 ohm-cm, can provide some protection from the ESD. Such conductive structures are often unduly complicated to employ and cannot be used in all magnetic structures. We believe, however, that the use of generally conductive protection structures will not reliably achieve sufficient ESD protection in successful, productive manufacturing processing. A substantial need remains for the development of other methods of protecting a magnetic recording head from ESD. In particular a substantial need exists for the development of structures and methods of protecting magnetic recording heads from the ESD that utilize structures that dissipate static charges without interfering with read/write operations.